The invention relates to a fire-retardant foam composite structure with a layer or layers having incorporated therein a brominated fire retardant.
Brominated compounds are commonly added to thermoplastic foams, particularly polystyrene foams, to enhance flame retardancy. Brominated compounds typically extinguish fire by decomposing and evolving bromine-containing gas upon exposure to high levels of heat or flames.
Brominated fire retardants have a tendency to form acidic decomposition products when exposed to elevated temperatures such as those encountered in thermoplastic foaming processes. These acidic decomposition products are usually not a problem unless they come into contact with water during the processing of molten thermoplastic resin prior to foaming of the resin. One instance when this may occur is when water is used as a primary or auxiliary blowing agent. Contact between the acidic decomposition products and the water blowing agent in the molten expandable thermoplastic resin causes the resin to be acidic and corrosive; this corrosiveness requires that expensive, acid-resistant equipment be used to make and process the expandable thermoplastic resin.
One solution to avoid the foam corrosiveness problem is to simply not use water as a blowing agent. Using water is desirable however, because water is inexpensive and environmentally friendly. Another solution would be to use a fire retardant that does not create acidic decomposition products like brominated compounds can. Replacement of brominated compounds is not desirable however, because they have proven to be both very effective and economical in use as fire retardants in thermoplastic foams.
Since it is desirable to use brominated compounds as fire retardants and water as a blowing agent in thermoplastic foams, it would be desirable to have a fire-resistant foam so structured to allow both to be used. It would be further desirable to have such a foam which can be processed without special manufacturing equipment, and which is both relatively simple and economical to make.